Multi-cable medical instrument

ABSTRACT

A medical instrument includes cable pairs respectively wound around input spindles and connected to actuate degrees of freedom of an instrument shaft structure. The cables may connect so that rotating the input spindles actuates corresponding degrees of freedom. First pulleys in the instrument may receive first cables from the input spindles and redirect the first cables toward the instrument shaft, and second pulleys may receive second cables from the input spindles and redirect the second cables toward the instrument shaft. In one configuration, the first and second pulleys are respectively mounted at first and second levels, and the second pulleys redirect the second cables through the first level. Additionally or alternatively, one level of cables may cross while the other level of cables does not.

RELATED APPLICATION

This patent application claims priority to and the filing date benefit of U.S. Provisional Patent Application No. 62/362,431, entitled “MULTI-CABLE MEDICAL INSTRUMENT” filed Jul. 14, 2016, which is incorporated by reference herein in its entirety.

BACKGROUND

Robotically controlled instruments such as employed for minimally invasive medical procedures often employ a tool or end effector or other manipulation element at the distal end of an extended instrument shaft. (As used herein, the terms “robot” or “robotically” and the like include teleoperation or telerobotic aspects.) The instrument shaft and the distal tool generally have small diameters, often less than a centimeter, to minimize the size of incisions or natural lumens needed for insertion of the instrument. Accordingly, the distal tools are often remotely operated or actuated via thin drive members (e.g., tendons or rods) that extend between the distal tool and a transmission, sometimes referred to as the backend mechanism of the instrument. The backend mechanism of a replaceable instrument is generally configured to removably couple to actuators (e.g., a motor pack) in a docking port of a robot. The robot can then control the actuators and apply force through the backend mechanism to the drive members and through the drive members to the distal tool of the instrument.

Medical instruments that have many degrees of freedom of movement typically require many drive members, and backend mechanisms that accommodate the transition from the layout of a docking port of a robot to the layout of the drive members in the instrument shaft can be complex and difficult to assemble.

SUMMARY

In accordance with an aspect of the invention, a medical instrument may provide efficient routing of actuation cables and relatively simple assembly process for complex medical instruments.

One specific implementation provides a medical instrument including a chassis, input spindles mounted in the chassis, upper and lower cables wound around the input spindles, and an instrument shaft extending from the chassis and including a mechanical structure providing multiple degrees of freedom of motion. The upper and lower cables may connect to the mechanical structure so that rotations of the input spindles actuate respective degrees of freedom. Lower pulleys may be mounted at a first level to receive the lower cables from the input spindles and to redirect the lower cables toward the instrument shaft. Upper pulleys may be mounted at a second level to receive the upper cables from the input spindles and redirect the upper cables through the first level and toward the instrument shaft.

Another specific implementation is a method for assembling a medical instrument. The method may include: mounting lower pulleys on a first piece of a chassis of the medical instrument; feeding lower cables from an instrument shaft of the medical instrument over the lower pulleys; attaching a second piece of the chassis to the first piece so that at least portions of the lower cables are between the lower pulleys and the second piece; mounting upper pulleys in positions such that the second piece is between the upper pulleys and the lower pulleys; and feeding upper cables from the instrument shaft over the upper pulleys.

Yet another specific implementation is a medical instrument including input spindles, lower cables respectively wound around the input spindles, upper cables respectively wound around the input spindles, and an instrument shaft extending from a chassis in which the input spindles are mounted. A mechanical structure on the instrument shaft has multiple degrees of freedom of motion, and the upper and lower cables connect to the structure such that rotations the input spindles respectively actuate the degrees of freedom. The lower or upper cables may extend between the input spindles and the instrument shaft without crossing, and paths of the other upper or lower cables cross between the input spindles and the instrument shaft. The crossing in one set of cables may allow the upper cable and the lower cable that wrap around the same input spindle to be more efficiently directed toward locations on opposite sides of a central axis of the instrument shaft, which may improve mechanical efficiency of actuation of the mechanical structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an implementation of a medical system employing removable instruments.

FIGS. 2A and 2B show side and top views of an example implementation of a medical instrument.

FIG. 3 shows cable routing in an example implementation of a backend mechanism of a medical instrument.

FIG. 4 is a cross-sectional view illustrating a routing of cables relative to a chassis and other structures in an example implementation of a backend mechanism of a medical instrument.

FIG. 5 is an expanded view of an implementation of a medical instrument including a backend mechanism with a multi-piece chassis.

FIGS. 6A, 6B, and 6C illustrate a pulley structure created during an assembly process for a backend mechanism that routes cables between an instrument shaft of a medical instrument and a set of input spindles around which the cables wrap.

FIG. 6D shows a cross-section of a portion of an example implementation of a backend mechanism and illustrates how pieces of a chassis may be fit close to a pulley to prevent cable derailment.

The drawings illustrate examples for the purpose of explanation and are not of the invention itself. Use of the same reference symbols in different figures indicates similar or identical items.

DETAILED DESCRIPTION

A backend mechanism of a robotically controlled medical instrument routes cables from multiple input spindles to an instrument shaft of the instrument and employs a routing that allows simple assembly using few components. Cables and associated pulleys in an instrument may be particularly grouped by level or height relative to the instrument shaft, and lower cables may be fit on pulleys mounted in a lower chassis piece before a next, higher chassis piece and pulleys for upper cables are attached to the lower chassis piece. A two-level system is particularly effective in a self-antagonistic system in which each input spindle has a pair of two associated cables that are wrapped around the input spindle in opposite directions and at different heights so that one cable pays in in one direction and the other cable pays out in an opposite direction as the spindle rotates. The cable routing leaves space for other components of the backend of a medical instrument, for example, to allow control or actuation of instrument shaft roll, grip drive, electrical connectors, and latching mechanisms that attach the backend mechanism to a robot. The cable routing can also position cables paired in opposition in the instrument shaft, so that the paired cables can efficiently actuate opposite directions of motion of a degree of freedom of the instrument.

FIG. 1 shows an example of a medical system 100 using replaceable medical instruments 110. System 100, which may, for example, be a da Vinci® Surgical System commercialized by Intuitive Surgical, Inc., may particularly employ multiple surgical instruments 110, each of which is removably mounted in a docking port 120 on a manipulator arm 130 of a robot 140. A sterile barrier (not shown) including a drape and adaptors for instruments 110 may be between instruments 110 and robot 140, so that robot 140, including manipulator arms 130 and docking ports 120, is outside a sterile environment for a patient. Accordingly, robot 140 may not need to be sterilized between medical procedures. In contrast, instruments 110, which may be used in the sterile environment and may contact the patient, are compact and removable so that instruments 110 may be sterilized or replaced between medical procedures performed using system 100.

Instruments 110 may vary in structure and purpose but may still be interchangeable, so that instruments 110 mounted in docking ports 120 of robot 140 can be selected for a particular medical procedure or changed during a medical procedure to provide the clinical functions needed. Each instrument 110 generally includes an end effector or distal tool 112, an instrument shaft 114, and a backend mechanism 116. Distal tools 112 may have different designs to implement many different functions. For example, distal tools 112 for different instruments 110 may have many different shapes or sizes and may include forceps, graspers, scalpels, scissors, cautery tools, or needle drivers to name a few possibilities, and instruments 110 having different distal tools 112 may be mounted on different arms 130 of robot 140 and may work cooperatively in the same work site. An endoscopic camera, for example, a stereoscopic camera, can also be mounted on an arm to provide visual information, particularly images, of the work site in which distal tools 112 of instruments 110 may be operating.

Docking ports 120 may include actuators, such as drive motors, that provide mechanical power for actuation of mechanical structures in instruments 110, drive couplings that connect the actuators to inputs of instruments 110, and systems for establishing and maintaining a sterile barrier between instruments 110 and the rest of medical system 100. Docking ports 120 may additionally include an electrical interface to provide power to instruments 110 or for communication with instruments 110, for example, to identify the type of instrument 110 in a docking port 120, to access parameters of instruments 110, or to receive information from sensors in instruments 110. For example, the electrical interface may convey to robot 140 measurements such as measurements of the position, orientation, or pose of distal tool 112 and instrument shaft 114 of an instrument 110. A computer system, which may be connected to or part of robot 140 and connected to a user interface device (not shown), may receive the measurements from instrument 110 and receive user commands from a surgeon or other medical personnel and may execute software that controls arms 130 and drive motors in docking ports 120 as needed to operate instruments 110 according to the user commands.

FIGS. 2A and 2B illustrate an example implementation of a medical instrument 110. FIG. 2A particularly shows a perspective view of an implementation having a tool 112 at the distal end of instrument shaft 114 and shows instrument shaft 114 extending from backend mechanism 116. In the illustrated implementation, distal tool 112 and instrument shaft 114 have six degrees of freedom of movement relative to backend mechanism 116. In particular, the six degrees of freedom correspond to: pitch and yaw rotations of a distal portion of tool 112 about two respective perpendicular axes 201 and 202 associated with a first joint mechanism 211 (also called “first joint 211”); pitch and yaw rotations or movement of jaws 213 relative to two respective perpendicular axes 203 and 204 associated with a second joint mechanism 212 (also called “second joint 212”; the joints 211, 212 are sometimes referred to as “wrists”); opening or closing movement 205 of jaws 213 for “grip” actuation; and “roll” rotations of instrument shaft 114 about its central length axis 206. Other instruments may have more, fewer, or different degrees of freedom of movement.

Backend mechanism 116 as shown in FIG. 2B has six input spindles 221 to 226 with engagement features that are shaped and positioned to engage actuators, e.g., drive motors, in a docking port of a robot. In general, each input spindle 221 to 226 may be coupled for actuation of a different degree of freedom of movement of the instrument, so that the robot can identify and use the correct actuator or actuators to rotate the spindle or spindles that exercise desired degrees of freedom of motion. The assignment input spindles 221 to 226 to corresponding degrees of freedom must be known to the robot but can be otherwise defined by an arbitrary standard or convention. In an exemplary implementation, input spindle 226 may couple to a roll mechanism that connects to a proximal end of instrument shaft 114 for rotation of instrument shaft 114 about its length axis 206 when input spindle 226 rotates. Input spindles 221 to 225 may couple to drive members (not shown) such as cables or rods extending though instrument shaft 114 to distal tool 112, so that the actuators in the robot can rotate input spindles 221 to 225 to control a distal mechanism including joints 211 and 212 and jaws 213. More specifically, in an exemplary implementation, rotation of input spindle 221 may control rotation or actuation of a distal portion of tool 112 about an axis 201. Rotation of input spindle 222 may control rotation about an axis 202. Rotation of input spindle 223 may control rotation about an axis 203 for yaw actuation of jaws 213, and rotation of input spindle 224 may control rotation about an axis 204 for pitch actuation of jaws 213. In some implementations, rotations of input spindles 221 to 226 may correspond to motion that is different from or more complex than simple rotations of structures about axes. For example, input spindle 225 may be coupled to jaws 213 through a push-pull rod for actuation of gripping with jaws 213. Also, in a particular implementation, the mechanism in tool 112 may couple a proximal portion of joint 212 to a distal portion of joint 211 for parallelogram motion, while the distal portion of joint 212 may move independently.

FIG. 3 shows selected elements within an implementation of the backend mechanism 116 of FIGS. 2A and 2B and particularly illustrates a routing in backend mechanism 116 of cables that run through instrument shaft 114 and connect to joints 211 and 212. The term “cable” is used herein in a broad sense to include any tendon-like structure. In particular, a length of cable in a medical instrument may include sections of different materials or different characteristics. A cable may include, for example, a stranded section where flexibility in the cable is desired (e.g., where the cable winds around a spindle, capstan, or pulley) and may include a more rigid section (e.g., a tube or rod) to limit stretching where less bending of the cable is needed. FIG. 3 does not show elements of backend mechanisms 116 that may be used for actuation of degrees of freedom associated with rotation of instrument shaft 114 or for opening and closing of jaws 213. Co-filed U.S. Pat. App. No. 62/362,340 (filed Jul. 14, 2016), entitled “GEARED ROLL DRIVE FOR MEDICAL INSTRUMENT”, and U.S. Pat. App. No. 62/362,365 (filed Jul. 14, 2016), entitled “GEARED GRIP ACTUATION FOR MEDICAL INSTRUMENTS”, disclose aspects of particular implementations of such mechanisms and are hereby incorporated by reference in their entirety.

Input spindles 221, 222, 223, and 224, as described above, are for actuation of degrees of freedom associated with respective axes 201, 202, 203, and 204, and each input spindles 221, 222, 223, and 224 includes a pair of capstans around which a pair of actuation cables are wrapped. For example, as shown in FIG. 3, an upper capstan 231A and a lower capstan 231B may be fixed on an axle of input spindle 221 so that both capstans 231A and 231B rotate with rotation of input spindle 221. (The terms upper and lower are used here to distinguish levels and may only apply literally when instrument shaft 114 points in a generally downward direction, as illustrated in FIG. 3.) A cable 241A wraps in one direction (e.g., clockwise or counterclockwise) around capstan 231A, and a cable 241B wraps in the opposite direction (e.g., counterclockwise or clockwise) around capstan 231B. Cable 241A extends from upper capstan 231A to an upper pulley 251 that directs cable 241A toward instrument shaft 114. Similarly, cable 241B extends from lower capstan 231B to a lower pulley 261 that directs cable 241B toward instrument shaft 114. Cables 241A and 241B extend from respective pulleys 251 and 261 through a guide 280, into instrument shaft 114, and through instrument shaft 114 to connect to actuated joint mechanism 211, so that pulling cable 241A or 242B rotates a distal portion of mechanism 211 (and distal portions of tool 112) about axis 201. The positions of pulleys 251 and 261 and the shape of guide 280 may position cables 241A and 241B on opposite sides of the center or length axis 206 of instrument shaft 114, which may allow cable 241A to efficiently drive motion of mechanism 211 in one direction or sense about axis 201 and also allow cable 241B to efficiently drive motion of mechanism 211 in an opposite direction or sense about axis 201.

Each input spindle 222, 223, or 224 similarly includes an axle through a pair of capstans 232A and 232B, 233A and 233B, or 234A and 234B around which a pair of cables 242A and 242B, 243A and 243B, or 244A and 244B wrap in opposite directions, and cables 242A, 242B, 243A, 243B, 244A, and 244B pass over respective pulleys 252, 262, 253, 263, 254, and 264 and run through guide 280 and instrument shaft 114. In an exemplary implementation, cables 242A and 242B connect to joint mechanism 211, and cables 243A, 243B, 244A, and 244B connect to joint mechanism 212.

Each pair of cables 242A and 242B, 243A and 243B, and 244A and 244B as described above includes one cable wound in one direction (e.g., clockwise) about an input spindle 221, 222, 223, or 224 and another cable wound in the other direction (e.g., counterclockwise) around the input spindle 221, 222, 223, or 224, so that rotation of an input spindle 221, 222, 223, or 224 pulls in one cable while paying out another cable. Accordingly, instrument 110 may employ self-antagonistic actuation in which each pair of cables 241A and 2416, 242A and 242B, 243A and 243B, or 244A and 244B controls a corresponding degree of freedom of movement, e.g., rotations about axes 201, 202, 203, or 204, of the instrument. Non-antagonistic cable actuation may be used in some embodiments (e.g., one cable per spindle).

In the illustrated system, mechanisms 211 and 212 are wrists or joints that each provide two degrees of freedom of movement. Many other mechanisms can provide one or more degrees of freedom of movement and may be connected so that one or more pairs of cables can respectively actuate the one or more degrees of freedom. An actuated mechanism may, for example, include a mechanical linkage with a link that is rotatable about a pivot, and a pair of cables may be connected to rotate the link in opposite directions relative to the pivot. Alternatively, actuated mechanisms may be any structure, e.g., a linkage, a slide, or a flexure, capable of being moved/actuated in opposite directions. For each pair of cables, pulling one cable may drive actuation of the corresponding degree of freedom in one direction or sense, and pulling the other cable in the pair may drive actuation of the corresponding degree of freedom in an opposite direction or sense.

Routing of cables 241A, 242A, 243A, and 244A employs upper pulleys 251, 252, 253, and 254 to receive cables 241A, 242A, 243A, and 244A from upper capstans 231A, 232A, 233A, and 234A and employs lower pulleys 261, 262, 263, and 264 to receive cables 241B, 242B, 243B, and 244B from respective lower capstans 231B, 232B, 2336, and 234B. Upper pulleys 251, 252, 253, and 254 may all be positioned at about the same common height, while lower pulleys 261, 262, 263, and 264 may all be positioned at about another common height that differs from the common height of upper pulleys 251, 252, 253, and 254. This allows the pulleys to be captured in stacked blocks or chassis pieces as described further below.

The arrangement of upper pulleys 251, 252, 253, and 254 and lower pulleys 261, 262, 263, and 264 may also be simplified by pairing pulleys to independently spin on shared axles. Using pulleys that share an axle may allow faster assembly, because multiple pulleys can be added to a structure by attaching a single axle. In the implementation of FIG. 3, input spindles 221, 222, 223 and 224 are arranged in a rectangular array, e.g., in rows and columns, and paths of cables from input spindles in the same row to locations over instrument shaft 114 are roughly parallel. Accordingly, pulleys 251 and 253, which guide cables 241A and 243A running at the same height and substantially the same direction from input spindles 221 and 223, can be mounted on a common axle 271. Similarly, upper pulleys 252 and 254, which guide cables 242A and 244A that emerge from input spindles 222 and 224 with substantially the same height and direction, can be mounted on a shared axle 272. Lower pulleys 262 and 264, which guide cables 242B and 244B that emerge from input spindles 222 and 224 with substantially the same height and direction, can be mounted on another shared axle (not visible in FIG. 3), and lower pulleys 261 and 263, which guide cables 241B and 243B that emerge from input spindles 222 and 224 with substantially the same path and direction can be mounted on yet another shared axle 274.

Pulley axles 271 to 274 may also be angled according to exit directions of the cables from the input spindles 221 to 224 and relative to the central axis 206 of instrument shaft 114. For example, axle 271 may be turned about a first axis (e.g., an axis parallel to the axles of input spindles 221 to 224) to minimize the fleet angles at pulleys 251 and 253 of cables 241A and 243A from input spindles 221 and 223. Axle 271 may be turned about a second axis (e.g., an axis approximately parallel to the portion of cables 241A and 243A between pulleys 251 and 253 and capstans 231A and 233A) so that the portion of cables 241A and 243A between pulleys 251 and 253 and guide 280 converge toward guide 280 and instrument shaft 114. The angling of axles 271 to 274 may reduce the average fleet angle for entry and exit of the cables from the upper and lower pulleys and thereby reduce friction and wear.

Axles 271 to 274 may further be positioned relative to input spindles 221 to 224 and instrument shaft 114 to minimize wrap angles across sliding surfaces on the pulleys. The positions of the pulleys may be further refined according to the desired cable paths exiting guide 280. In particular, redirection of any cable passing through guide 280 should only cause rubbing on the resilient surface (e.g., a metal portion) of guide 280 and not a softer surface (e.g., a plastic portion) of guide 280. The wrap angle across guide 280 should also be small so that the friction and sawing action any cable against guide 280 is small. The cable path should further be relatively direct so that length of stranded cable does not negatively affect the overall stiffness of the drive train between the corresponding input spindle and the actuated mechanism. In general, the stranded sections of cables tend to stretch more than the rigid hypotube sections used in some embodiments.

The separations between input spindles 221 to 224 may be considerably larger than the diameter of instrument shaft 114 into which the cables need to be directed. Accordingly, the paths of the cables need to converge between input spindles 221 to 225 and instrument shaft 114. The cables also should not rub against each other or against any other structures in backend mechanism 116. To avoid cable interference, the winding directions of cables 241A, 241B, 242A, 242B, 243A, 243B, 244A, and 244B around the input spindles in the illustrated implementation are chosen so that cables at one level (e.g., lower cables 241B, 242B, 243B and 244B) emerge from inside the array of input spindles 221 to 224, and cables at other levels(e.g., upper cables 241A, 242A, 243A and 244A) emerge from an outer edge of the array of input spindles. Lower cables 241B, 242B, 243B and 244B, which emerge from inside an area of the input spindle array, can directly converge at a relatively small angles toward instrument shaft 114 without interfering with each other or rubbing against other structures, such as input spindles 223 or 224. Upper cables 241A, 242A, 243A and 244A, which emerge from the outer edge of input spindles 221 to 224, have crossing paths, which increases the angle of convergence. In particular, upper cables 241A and 243A, which emerge from input spindles 221 and 223, cross over upper cables 242A and 244A, which emerge from input spindles 222 and 224. For the crossing pattern, upper pulleys 251 and 253, which are within the same level group as upper pulleys 252 and 254, although having a generally common height may be staggered in height (e.g., so that cables 241A and 243A can cross over cables 242A and 244A without rubbing). The larger angle of convergence provided by the crossing pattern allows cables 241A and 242A to pass from outer edges of input spindles 221 and 222 through the gap between input spindles 223 and 224. The crossing pattern also allows pulleys 251 and 253, which receive cables 241A and 243A, to be farther from pulleys 252 and 254, which receive cables 242A and 244A, than pulleys 261 and 263 are from pulleys 262 and 264. The wider spacing of upper pulleys 251 to 254 allows routing cables 241A to 244A toward instrument shaft 114 without interference from lower pulleys 261 to 264 or cables 241B to 244B. Crossing one level of cables in this fashion also allows positioning of cables that wrap about the same input spindle and that are therefore paired for actuation of the same degree of freedom in opposition in instrument shaft 114, which may permit efficient connection of the pair of cables to an actuated mechanism.

The cable routing in the implementation of FIG. 3 may provide several advantages. In particular, the difference in the horizontal separation of upper pulleys 251 to 254 from the horizontal separation of lower pulleys 261 to 264, may allow upper pulleys 251 to 254 to be vertically positioned closer to lower pulleys 261 to 264, e.g., at a vertical separation that is less than the diameter of pulleys 251 to 254 and 261 to 264. Also, upper pulleys 251 to 254 and lower pulleys 261 to 264 may be at the same distance from the closest input spindles 223 and 224. Since one group of pulleys is not required to be closer to the input spindles, all of the pulleys can be at a relatively long distance from the input spindles, which may minimize the splay angles for the actuation cables. A crossing cable pattern may further reduce the space needed to accommodate the required splay. The cable routing can position pulleys so that the cables do not rub on each other or on neighboring input spindles and do not require additional intermediary idler pulleys.

FIG. 4 shows a cross-sectional view of internal structure in an example implementation of a backend mechanism 116. As illustrated, backend mechanism 116 may include a chassis 500 with a central support structure 410 that extends between rows of input spindles 221, 222, 223, and 224. The routing of cables 241A to 244A or 241B to 244B allows use of central support structure 410 to strengthen chassis 500 without interfering with cables 241A to 244A or 241B to 244B. The cable routing also causes cables 241A to 244A or 241B to 244B to converge sufficiently to pass between input spindles 225 and 226, through an opening in a linkage 420 for actuation of jaws 213, and through an opening in a linkage 430 used for actuation of rotation about instrument shaft axis 206. This configuration with support structure 410 in the center of backend mechanism 116 opens up access to input spindles 221, 222, 223, and 224 from around the perimeter of chassis 500, for example, to attach and wrap cables 241A to 244A or 241B to 244B on capstans 231A to 234A and 231B to 234B and to tighten capstan clamping screws during assembly of backend mechanism 116. Once input spindles 221, 222, 223, and 224 are mounted in chassis 500 and capstans 231A to 234A and 231B to 234B are wrapped and clamped, the space around input spindles 221, 222, 223, and 224 is available for other structures, such as a structure 440, for latching backend mechanism to a docking port on a robot.

FIG. 5 shows an expanded view of some of the components in an implementation of a medical instrument with a multi-piece chassis 500 for a backend mechanism 116. Chassis 500 includes pieces 510, 520, 530, 540, 550 and 560 that may be snapped together during an assembly process. During the assembly process, a proximal end of instrument shaft 114 may be inserted in a bearing system in chassis piece 510, at which point cables, e.g., cables 241A to 244A and 241B to 244B, which are attached to the distal tool of the instrument extend from instrument shaft 114. The cables may then be fed through desired locations in guide 280, and chassis piece 520 may be attached to chassis piece 510 so that guide 280 is captured between chassis pieces 510 and 520. All or portions of grip or roll gears or mechanisms that couple to input spindles 225 or 226 may also be assembled on chassis pieces 510 and 520 before chassis pieces 510 and 520 are snapped together and may be held in place by chassis pieces 510 and 520. An upper portion of chassis piece 520 further includes central support structure 410, which is described above and includes features 524 shaped to hold lower capstans 231B to 234B which will be mounted on input spindles 221 to 224.

The assembly process can then connect chassis piece 530 to chassis piece 520. Chassis pieces 530 and 520 are separate to allow for the assembly of linkage 420 that couples to input spindle 525 and is employed for grip actuation in the exemplary implementation.

Chassis piece 530 has an upper portion shaped to hold axles 273 and 274 for lower pulleys that guide the actuation cables and redirect the actuation cables toward the instrument shaft. As shown in FIG. 6A, lower pulleys 263 and 261 on axle 273 may be mounted in slots formed in chassis piece 530. Similarly, lower pulleys 262 and 264 on axle 274 are mounted in another set of slots in chassis piece 530. Lower cables 241B, 242B, 243B, and 244B, which extend from instrument shaft 114, may be seated in grooves on respective lower pulleys 261, 262, 263, and 264 and threaded through openings in chassis piece 530 so that proximal ends of lower cables 241B, 242B, 243B, and 244B are near features 524 where input spindles 221 to 224 will reside.

The assembly process can next connect a chassis piece 540 to chassis piece 530 as shown in FIG. 6B. Chassis piece 530 and 540 may be shaped to provide a close fit between chassis piece 540 and pulleys 261 to 264 so that cables 241B, 242B, 243B, and 244B are not easily derailed. Upper pulleys 251 and 253 on axle 272 and upper pulleys 252 and 254 on axle 271 may be mounted in slots created by the combination of chassis pieces 530 and 540. The slot into which axle 271 fits may be at slightly different level from the slot into which axle 272 fits so that the upper cables can cross as described above. Upper cables 241A, 242A, 243A, and 244A may be seated on respective upper pulleys 251, 252, 253, and 254 and threaded through openings in chassis 500 so that proximal ends of upper cables 241A, 242A, 243A, and 244A are also near features 524. A chassis piece 550 connects to chassis pieces 530 and 540 as shown in FIG. 6C and may be shaped to provide a close fit to upper pulleys 251 to 254 so that upper cables 241A, 242A, 243A, and 244A are not easily derailed. FIG. 6D particularly shows a cross-sectional view illustrating how chassis piece 550 when mounted on pieces 530 and 540 may be close fit to pulley 251 so that a gap 545 between chassis piece 550 and pulley 251 is narrower than the thickness of cable 241A on pulley 251. As a result, cable 241A fits into the grove in pulley 251 and cannot slip through gap 545.

Returning to FIG. 5, a chassis piece 560 snaps onto or otherwise connects to one or more of chassis pieces 520, 530, and 550. The top of chassis piece 560 is shaped to fit a docking port of a robot and includes features 564 that are shaped and located to hold the engagement features of input spindles 221 to 224 of the instrument. When chassis piece 560 attaches to the assembly including pieces 510, 520, 530, 540, and 550, chassis 500 may capture input spindles 221 to 224 between features 564 on chassis piece 560 and features 524 on chassis piece 520. Each input spindle may include an axle and a pair of capstans, e.g., upper capstans 231A to 234A and lower capstans 231B to 234B, which are initially free to rotate relative to each other. The loose proximal ends of the actuation cables near features 524 may be attached to the corresponding one of capstans 231A to 234A or 231B to 234B. Each capstan can then be independently rotated to wind the attached cable in the desired direction and to take up slack and provide a desired pre-tension in the attached cable. Once both cables wrapped around an input spindle have the desired cable tensioning, the capstans can be clamped or locked in place on the axle of the input spindle, e.g., by tightening a clamping screw. Other structures such as release levers comprising structure 440 of FIG. 4 may wrap around the outside of the actuation structure and cables and may be installed after assembly of the input spindles and routing of cables. Co-filed U.S. Pat. App. No. 62/362,454 (filed Jul. 14, 2016), entitled “INSTRUMENT RELEASE”, describes structures such as release levers comprising structure 440 in more detail and is hereby incorporated by reference in its entirety.

The instrument assembly and cable routing process illustrated by FIGS. 5 and 6A to 6D may be relatively simple when compared to the complexity of the instrument. In particular, achieving the desired cable routing does not require simultaneous threading of cables through and around a complex sequence of structures from which the cables may slip. Instead, assembly can proceed in a series of simple steps with the cables being in a secure configuration after each step. Further, the shape of the chassis provides good access to input spindles for cable connections.

Although particular implementations have been disclosed, these implementations are only examples and should not be taken as limitations. Various adaptations and combinations of features of the implementations disclosed are within the scope of the following claims. For example, although embodiments that employ rotating spindles have been described, other means of controlling cable motion may be used. These means include, for example, sliding tabs, levers, gimbals, and the like. 

1. A medical instrument comprising: a plurality of input spindles; a plurality of first cables; a plurality of second cables, one of each cable of the first and second plurality of cables being wrapped around a corresponding input spindle of the plurality of input spindles; a chassis in which the plurality of input spindles is mounted; an instrument shaft comprising a first end and a second end, the instrument shaft extending from the chassis at the first end; a mechanical structure coupled to the second end of the instrument shaft, the mechanical structure having a plurality of degrees of freedom of motion, the plurality of first cables and the second cables being connected to the mechanical structure such that rotations of the plurality of input spindles actuate the plurality of degrees of freedom; a plurality of first pulleys mounted at a first level on the chassis, the plurality of first pulleys receiving the plurality of first cables from the plurality of input spindles and redirecting the plurality of first cables toward the instrument shaft; and a plurality of second pulleys mounted at a second level on the chassis different from the first level, the plurality of second pulleys receiving the plurality of second cables from the plurality of input spindles and redirecting the plurality of second cables through the first level and toward the instrument shaft.
 2. The medical instrument of claim 1, wherein the chassis comprises: a first piece on which the plurality of first pulleys is mounted; and a second piece mounted over the first piece so that the plurality of first pulleys is located between the first piece and the second piece, the second piece being between the plurality of first pulleys and the plurality of second pulleys.
 3. The medical instrument of claim 1, wherein: the plurality of first cables extends between the plurality of input spindles and the plurality of first pulleys without crossing; and a first set of the plurality of second cables crosses a second set of the plurality of second cables between the plurality of input spindles and the plurality of second pulleys.
 4. The medical instrument of claim 3, wherein: for each individual spindle of the plurality of input spindles, the first cable and the second cable wrapped around the individual input spindle are directed toward locations on opposite sides of a central axis of the instrument shaft.
 5. The medical instrument of claim 3, wherein: the plurality of input spindles is arranged in an array; each first cable of the plurality of first cables is wrapped about the corresponding input spindle in a direction such that a path of the first cable from the corresponding input spindle to the plurality of first pulleys emerges within the array; and each second cable of the plurality of second cables is wrapped about the corresponding input spindle in a direction such that a path of the second cable from the corresponding input spindle to the plurality of second pulleys emerges from a perimeter of the array.
 6. The medical instrument of claim 1, wherein: for each corresponding input spindle of the plurality of input spindles, the first cable wraps around the corresponding input spindle in a first direction, and the second cable wraps around the corresponding input spindle in a second direction opposite the first direction.
 7. A method for assembling a medical instrument comprising: mounting a plurality of first pulleys on a first piece of a chassis of the medical instrument; feeding a plurality of first cables from an instrument shaft of the medical instrument over the plurality of first pulleys; attaching a second piece of the chassis to the first piece so that at least a portion of the plurality of first cables is between the plurality of first pulleys and the second piece; mounting a plurality of second pulleys on the chassis in positions such that the second piece is between the plurality of second pulleys and the plurality of first pulleys; and feeding a plurality of second cables from the instrument shaft over the plurality of second pulleys.
 8. The method of claim 7, wherein: gaps between the second piece and the plurality of first pulleys are narrower than a width of the plurality of first cables.
 9. The method of claim 7, further comprising: attaching a third piece of the chassis to the first and second pieces so that at least a portion of the plurality of second cables is between the plurality of second pulleys and the third piece.
 10. The method of claim 7, further comprising: winding a first cable of the plurality of first cables around a lower portion of an input spindle; and winding a second cable of the plurality of second cables around an upper portion of the input spindle, wherein the second cable and the first cable wrap around the input spindle in opposite directions.
 11. The method of claim 10, wherein winding the first cable around the input spindle comprises: winding the first cable on a first capstan until the first cable has a desired tension, and affixing the first capstan on the input spindle.
 12. (canceled)
 13. The instrument of claim 1, wherein: for each corresponding input spindle of the plurality of input spindles, the first cable and the second cable wrapped around the corresponding input spindle are directed toward locations on opposite sides of a central axis of the instrument shaft.
 14. The instrument of claim 1, wherein: the plurality of input spindles is arranged in an array; the plurality of first cables are wrapped about the plurality of input spindles in directions such that paths of the plurality of first cables leading from the plurality of input spindles to the plurality of first pulleys emerge within the array; and the plurality of second cables are wrapped about the plurality of input spindles in directions such that paths of the plurality of second cables leading from the plurality of input spindles to the plurality of second pulleys emerge from a perimeter of the array.
 15. A medical instrument comprising: a chassis comprising a first piece and a second piece positioned over the first piece, the first piece of the chassis comprising a first pulley, and the second piece of the chassis comprising a second pulley; a shaft comprising a first end and a second end, the first end of the shaft being coupled to the chassis; a jointed mechanism coupled to the second end of the shaft, the jointed mechanism having a mechanical degree of freedom; means for pulling a first cable, the first cable extending from the means for pulling the first cable, across the first pulley, through the shaft, and to the jointed mechanism; and means for pulling a second cable, the second cable extending from the means for pulling the second cable, across the second pulley, through the shaft, and to the jointed mechanism; wherein the first and second cables actuate the mechanical degree of freedom of the jointed mechanism.
 16. The medical instrument of claim 15, wherein: the first piece of the chassis comprises a third pulley; the second piece of the chassis comprises a fourth pulley; the jointed mechanism has a second mechanical degree of freedom; and the medical instrument further comprises: means for pulling a third cable, the third cable extending from the means for pulling the third cable, across the third pulley, through the shaft, and to the jointed mechanism; means for pulling a fourth cable, the fourth cable extending from the means for pulling the fourth cable, across the fourth pulley, through the shaft, and to the jointed mechanism; wherein the third and fourth cables actuate the second mechanical degree of freedom of the jointed mechanism.
 17. The medical instrument of claim 16, wherein: the second cable crosses the first cable between the means for pulling the second cable and the second pulley.
 18. The medical instrument of claim 16, wherein: the second cable crosses the first cable and the fourth cable between the means for pulling the second cable and the second pulley.
 19. The medical instrument of claim 16, wherein: the second cable crosses the first cable and the fourth cable between the means for pulling the second cable and the second pulley; and the fourth cable crosses the second cable and the third cable between the means for pulling the fourth cable and the fourth pulley.
 20. The medical instrument of claim 15: wherein the means for pulling the first cable and the means for pulling the second cable is a spindle around which the first cable is wrapped in a first direction and the second cable is wrapped in a second direction opposite the first direction.
 21. The medical instrument of claim 15: wherein the means for pulling the first cable comprises a first spindle around which the first cable is wrapped; and wherein the means for pulling the second cable comprises a second spindle around which the second cable is wrapped. 